1. Field of the Invention
The present invention is directed to an x-ray diagnostics installation of the type wherein the x-ray image is converted through a video chain to a displayable video image.
2. Description of the Prior Art
An x-ray installation is known from German OS 32 25 061, corresponding to U.S. Pat. No. 4,517,594, discloses an x-ray diagnostics installation wherein a portion of the output image from the x-ray image intensifier is coupled through a light distributor onto a detector consisting of a matrix of photosensors. The parallel outputs of the photosensors are connected to a summing amplifier via switches. The output signals of the individual photodetectors can be weighted by variable resistors. The output signal of the summing amplifier is compared, as an actual value signal, to a rated value, and the high voltage generator for the x-ray source is switched and controlled on the basis of the comparison.
A disadvantage of the above installation is the necessity of providing a light distributor. Moreover, it is relatively complex to use a matrix consisting of photosensors, because an amplifier must be allocated to each photosensor. Since the amplifiers require a certain amount of space, the resolution of the image which is achievable is limited, because only a limited number of photosensors can be used within a given area. Additionally, even though variable resistors are used, these resistors, once set, do not change in value, therefore a continuous variation and matching of the weighting cannot be undertaken.